I believe this is a known issue that is scheduled to be resolved in an upcoming release in the near future. If it is still not resolved after upgrading to the next released maintenance release, then I would recommend sending this in to our support team at support@tableausoftware.com

The issue that you are encountering is a manifestation of a known issue. Our engineering developed a fix for the issue in 7.04. Please upgrade to the latest maintenance release of Tableau Server to get advantage of the fixes made. Please refer to he following articles to upgrade:

In case by some reason upgrade is not possible this issue can be resolved in the short-term by re-publishing the workbook or restarting Tableau Server.

If you continue to experience the issue after installing the maintenance release that includes the fix, please let us know.

Thank you for your patience.

Also I am excited to announce our Tableau Customer Conference for 2012. If you came to any of the previous years, you know what an amazing experience the conference is. I would like to see you at the conference this year.